Unraveling the synergy: How electron beam irradiation potentiates citric acid modification of chitosan and dictates its functional properties

This study proposes a novel method for efficiently modifying native chitosan (NCS) by employing electron beam irradiation (EBI) in conjunction with citric acid (CA)-associated modification, thereby overcoming the limitations of NCS application, including poor solubility and restricted functionality. The results confirmed that EBI effectively reduced the apparent viscosity-average molecular weight of NCS and exposed more accessible sites, thereby facilitating subsequent CA-associated modification. Comprehensive analyses (FT-IR, XRD, DSC, and SEM) confirmed that the synergy of physical activation and chemical modification disrupted the hydrogen-bond network of NCS at the molecular level and reduced its crystallinity. These structural changes generated a porous morphology and significantly improved pH-dependent solubility stability, thereby preventing precipitation in neutral to alkaline environments. Antioxidant and antibacterial properties are also enhanced, which may be attributed to exposed active sites, CA-associated groups, and improved solution clarity. Ultimately, NCS derivatives with improved pH-dependent solubility stability, strong antioxidant activity, and excellent antibacterial performance were obtained. PCA suggested an association between apparent viscosity-average molecular weight reduction and functional improvement. These findings provide a feasible strategy for improving the applicability of chitosan in food-related systems.